docs: def diffuser_conical_staged(Di1, Di2, DEs, ls, fd=None, method='Rennels'):
      r'''Returns loss coefficient for any series of staged conical pipe expansions
      as shown in [1]_. Five different formulas are used, depending on
      the angle and the ratio of diameters. This function calls diffuser_conical.
  
      Parameters
      ----------
      Di1 : float
          Inside diameter of original pipe (smaller), [m]
      Di2 : float
          Inside diameter of following pipe (larger), [m]
      DEs : array
          Diameters of intermediate sections, [m]
      ls : array
          Lengths of the various sections, [m]
      fd : float
          Darcy friction factor [-]
      method : str
          The method to use for the calculation; one of 'Rennels', 'Crane',
          'Miller', 'Swamee', or 'Idelchik' [-]
  
      Returns
      -------
      K : float
          Loss coefficient [-]
  
      Notes
      -----
      Only lengths of sections currently allowed. This could be changed
      to understand angles also.
  
      Formula doesn't make much sense, as observed by the example comparing
      a series of conical sections. Use only for small numbers of segments of
      highly differing angles.
  
      Examples
      --------
      >>> diffuser_conical(Di1=1., Di2=10.,l=9, fd=0.01)
      0.973137914861591
  
      References
      ----------
      .. [1] Rennels, Donald C., and Hobart M. Hudson. Pipe Flow: A Practical
         and Comprehensive Guide. 1st edition. Hoboken, N.J: Wiley, 2012.
      '''
      K = 0
      DEs.insert(0, Di1)
      DEs.append(Di2)
      for i in range(len(ls)):
          K += diffuser_conical(Di1=float(DEs[i]), Di2=float(DEs[i+1]), l=float(ls[i]), fd=fd, method=method)
      return K